1. Field of the Invention
This present invention relates to surgical robots and particularly to control methods for operating such robots.
2. Description of the Prior Art
Robotic systems have been used in clinical practice for over twenty years, during which time much progress has been made in the theory, technique and clinical applications of surgical robotics. While the robots initially used for surgical applications were industrial robots, dedicated robots have since been developed that are specifically designed to meet the specialized needs of surgery.
Industrial robots are designed for use in a structured environment, i.e., one in which every element is fixed. Such robots thus perform pre-programmed tasks repeatedly, without allowing for human intervention. The environment in a surgical operation, by contrast, is totally unstructured because body sizes differ among different patients, and because different operations tend to involve different and complex procedures. A surgical robot must be adaptable to these differences, and surgeons and their medical staffs must be able to intervene with and work closely with the robot. To adapt to the unique requirements of surgical operations, a surgical robot should thus be adaptable to different patients and different procedures and should be able to complement human abilities and trained skills. A surgical robot must also consume as small a space in an operating room as possible in order to minimize interference with the medical staff.
Medical Robotics of Stockholm, Sweden (http://www.medicalrobotics.se), supplies a surgical robot under the name “PinTrace” for use in orthopaedic surgery. This robot has an anthropomorphic structure with six revolute joints to provide a big workspace. Mazor Robotics Ltd. of Israel (http://www.mazorrobotics.com) supplies a surgical robot called “SpineAssist” for use in minimally invasive spine surgery. This is a miniature parallel robot with six degrees of freedom which is mounted on the spine during the surgery.
Control of a surgical robot is important in providing the robot with both utility and safety. Typical robotic systems have one of three control modes. The first is a passive control in which the robot is operated manually. The second is an active control in which the robot can move autonomously according to a pre-programmed trajectory. The third one is a tele-operation mode, in which the robot is controlled in real-time in response to on-line direct orders from the operator.
The TIMC Laboratory (France) (http://www-timc.imag.fr) offers a robot arm named “PADyC” for Cardiac Surgery Applications. This robot operates as a passive guide with dynamic constraints which limit the instrument motions according to a pre-defined surgical plan. Curexo Technology (Fremont, Calif., USA) offers the “ROBODOC” system for joint replacement surgery. This system can cut bone automatically, but the interaction between cutting tools and patient is controlled only by computer. Intuitive Surgical, Inc. (Sunnyvale, Calif., USA) (http://www.intuitivesurgical.com), offers a surgical robot for endoscopic surgery under the name “Da Vinci.” This robot has three to four robot arms, and the surgeon can control these robot arms through tele-operation controllers.